Secondary structure of food proteins by Fourier transform spectroscopy in the mid-infrared region

Fourier transform spectroscopy in the mid-infrared (400–5,000 cm⁻¹) (FT-IR) is being recognized as a powerful tool for analyzing chemical composition of food, with special concern to molecular architecture of food proteins. Unlike other spectroscopic techniques, it provides high-quality spectra with very small amount of protein, in various environments irrespective of the molecular mass. The fraction of peptide bonds in α-helical, β-pleated sheet, turns and aperiodic conformations can be accurately estimated by analysis of the amide I band (1,600–1,700 cm⁻¹) in the mid-IR region. In addition, FT-IR measurement of secondary structure highlights the mechanism of protein aggregation and stability, making this technique of strategic importance in the food proteomic field. Examples of applications of FT-IR spectroscopy in the study of structural features of food proteins critical of nutritional and technological performance are discussed.     

Enhancing the stress responses of probiotics for a lifestyle from gut to product and back again

Before a probiotic bacterium can even begin to fulfill its biological role, it must survive a battery of environmental stresses imposed during food processing and passage through the gastrointestinal tract (GIT). Food processing stresses include extremes in temperature, as well as osmotic, oxidative and food matrix stresses. Passage through the GIT is a hazardous journey for any bacteria with deleterious lows in pH encountered in the stomach to the detergent-like properties of bile in the duodenum. However, bacteria are equipped with an array of defense mechanisms to counteract intracellular damage or to enhance the robustness of the cell to withstand lethal external environments. Understanding these mechanisms in probiotic bacteria and indeed other bacterial groups has resulted in the development of a molecular toolbox to augment the technological and gastrointestinal performance of probiotics. This has been greatly aided by studies which examine the global cellular responses to stress highlighting distinct regulatory networks and which also identify novel mechanisms used by cells to cope with hazardous environments. This review highlights the latest studies which have exploited the bacterial stress response with a view to producing next-generation probiotic cultures and highlights the significance of studies which view the global bacterial stress response from an integrative systems biology perspective.     

Drought-Tolerance of Wheat Improved by Rhizosphere Bacteria from Harsh Environments: Enhanced Biomass Production and Reduced Emissions of Stress Volatiles

Water is the key resource limiting world agricultural production. Although an impressive number of research reports have been published on plant drought tolerance enhancement via genetic modifications during the last few years, progress has been slower than expected. We suggest a feasible alternative strategy by application of rhizospheric bacteria coevolved with plant roots in harsh environments over millions of years, and harboring adaptive traits improving plant fitness under biotic and abiotic stresses. We show the effect of bacterial priming on wheat drought stress tolerance enhancement, resulting in up to 78% greater plant biomass and five-fold higher survivorship under severe drought. We monitored emissions of seven stress-related volatiles from bacterially-primed drought-stressed wheat seedlings, and demonstrated that three of these volatiles are likely promising candidates for a rapid non-invasive technique to assess crop drought stress and its mitigation in early phases of stress development. We conclude that gauging stress by elicited volatiles provides an effectual platform for rapid screening of potent bacterial strains and that priming with isolates of rhizospheric bacteria from harsh environments is a promising, novel way to improve plant water use efficiency. These new advancements importantly contribute towards solving food security issues in changing climates.     

拉曼光谱检测微生物的研究方法和进展北大核心

快速准确地识别和鉴定微生物对于环境科、食品质量以及医学诊断等领域研究至关重要。拉曼光谱(Raman spectroscopy)已经被证明是一种能够实现微生物快速诊断的新技术,在提供微生物指纹图谱信息的同时,能够快速、非标记、无创、敏感地在固体和液体环境中实现微生物单细胞水平的检测。本文简单介绍了拉曼光谱的基本概念和原理,重点综述了拉曼光谱微生物检测应用中的样品处理方法及光谱数据处理方法。除此之外,本文概括了拉曼光谱在细菌、病毒和真菌中的应用,其中单独概括了拉曼在细菌快速鉴定和抗生素药敏检测中的应用。最后,本文阐述了拉曼光谱在微生物检测中的挑战和展望。     

Innate and specific gut-associated immunity and microbial interference

Certain bacterial species isolated from the gastrointestinal microbial communities release low-molecular-weight peptides into milk products using bacteria-derived proteases that degrade milk casein, and thereby generate peptides, triggering immune responses. The intestinal microbial communities contributes to the processing of food antigens in the gut. The present study was designed to investigate the immunomodulatory effects of microbial interference to determine whether casein degraded by probiotic bacteria-derived enzymes could modulate the cytokine production and peripheral blood mononuclear cells in atopic infants with cow or other synthetic milk allergy. Without hydrolyzation, casein reduced the production of interleukin-4, which indicates that probiotics modify the structure of potentially harmful antigens and thereby alter the mode of their immunogenicity. Intraluminal bacterial antigens have been reported to elicit specific responses in the gut-associated lymphoid tissue (GALT) through the binding capacity of intraluminal bacterial antigens to epithelial cells, which allows antigen entry via enterocytes and aids in evading the tolerance function in Peyer's patches. Such tonic immune responses in the GALT may allow control of the metabolic activity and balance of the gut microbial communities.     

The detection of food soils on stainless steel using energy dispersive X-ray and Fourier transform infrared spectroscopy

Organic soiling is a major issue in the food processing industries, causing a range of biofouling and microbiological problems. Energy dispersive X-ray (EDX) and Fourier transform infra red spectroscopy (FT-IR) were used to quantify and determine the biochemical groups of food soils on stainless steel surfaces. EDX quantified organic material on surfaces where oily based residues predominated, but was limited in its usefulness since other food soils were difficult to detect. FT-IR provided spectral 'fingerprints' for each of the soils tested. Key soiling components were associated with specific peaks, viz. oils at 3025 cm(-1)-3011 cm(-1), proteins at 1698 cm(-1)-1636 cm(-1) and carbohydrates at 1658 cm(-1)-1596 cm(-1), 783 cm(-1)-742 cm(-1). High concentrations of some soils (10%) were needed for detection by both EDX and FT-IR. The two techniques may be of use for quantifying and identifying specific recalcitrant soils on surfaces to improve cleaning and hygiene regimes.     

Analysis of covariance patterns in gene expression data and FT-IR spectra

The aim of this study was to detect and interpret correlation patterns in several large data matrices from the same biological system using Partial Least Squares Regression (PLSR) in order to get information on the system under investigation. To do this, DNA microarray data and Fourier Transform Infrared (FT-IR) spectra from a designed study where Campylobacter jejuni was exposed to environmental stress conditions, were used. The experimental design included variation in atmospheric conditions, temperature and time. PLSR was first used to analyse each of the two data types separately in order to explore the effect of the experimental parameters on the data. The results showed that both the gene expression and FT-IR spectra were affected by the variations in atmosphere, temperature and time, but that the effect was different for the two types of data. When the DNA microarray data and FT-IR spectra were linked together by PLSR, covariation due to temperature was seen. Both specific genes and ranges in the FT-IR spectra that were connected to the variation in temperature were detected. Some of these are possibly connected to properties of the cell wall of the bacteria. The results in this study show the potential of PLSR for investigation of covariance structures in biological data. By doing this, valuable information about the biological system can be detected and interpreted. It was also shown that the use of FT-IR spectroscopy provided important information about the stress responses in the bacteria, information that was not detected from the DNA microarray data.     

Preparation and Characterization of Self-Reinforced Antibacterial and Oil-Resistant Paper Using a NaOH/Urea/ZnO Solution

This paper describes self-reinforced antibacterial and oil-resistant properties that were successfully prepared by surface selective dissolution of filter paper in a NaOH/Urea/ZnO (weight ratio of 8:12:0.25) aqueous solution. The effect of the processing time on the mechanical properties of this paper was evaluated at -12°C. The paper morphologies were characterized using Scanning Electron Microscopy (SEM), X-ray Diffraction (XRD), Fourier Transform Infrared Spectroscopy (FT-IR) and X-ray photoelectron spectroscopy (XPS). The oil-resistance and antibacterial properties of the produced paper were also investigated. Excellent mechanical properties were observed for an optimized handling time. The tensile and burst strengths of the modified paper were in excess of 100% of the original. Meanwhile, the treated paper was completely oil-resistant within 24 h and demonstrated good antibacterial properties when exposed to Staphylococcus aureus. The traces of residual zinc oxide were found to be safe for food.     

Vibrational spectroscopy and X-ray diffraction methods to establish the differences between hardwood and softwood

FT-IR spectrometry and X-ray diffraction were applied to probe the differences between pulp fibers from Eucalyptus wood (hardwood) and Norway spruce wood (softwood). Wood processing was found to induce certain structural alterations within its components depending on the type of wood and the applied procedure. These differences were established by using techniques such as; spectral comparison of wood samples with those of individual component fractions, derivative spectroscopy, bands deconvolution, etc. FT-IR spectroscopy was shown to be an important tool that provided details about the structural characteristics of hardwood and softwood samples. Using second-derivative spectra and deconvolution processes small differences between spectra became apparent that allowed correlations to be made related to wood composition. In addition a correlation was established between the integral absorptions for the various bands and lignin content as well as the lignin/carbohydrate content. Relations between various spectral characteristics and the degree of crystallinity and sample composition were established.     

Regulation of bacterial assemblages in oligotrophic plankton systems: results from experimental and empirical approaches

Bacteria are relevant members of planktonic food webs, both in terms of biomass and production share. The assessment and comprehension of the factors that control bacterial abundance and production are, thus, necessary to understand how carbon and nutrients circulate in planktonic food webs. It is commonly believed that bacterial abundance, activity and production are either determined by the available nutrient levels (‘bottom-up’ control) or by the effect of predators (‘top-down’). These factors have also been shown to regulate the internal structure (the physiological and phylogenetic structure) of the bacterioplankton black box. We present here different empirical and experimental ways in which the factors that control bacterial communities are assessed, among them, the direct comparison of the rates of bacterial growth and losses to grazing. Application of several of these methods to open ocean data suggests that bacteria are regulated by resources at the largest scales of analysis, but that this overall regulation is strongly modulated by predators in all types of systems. In the most oligotrophic environments, bacterial abundance and growth are regulated by predators, while in the richest environments it is bacterial (phylogenetic, size, activity) community composition that is most affected by protist predators, while abundance can be influenced by metazoans. Because changes in bacterial community composition require that bacteria have enough nutrient supply, the overall effect of these regulations is that bacterial growth appears to be top-down regulated in the most nutrient-poor environments and bottom-up regulated in the richer ones. This revised version was published online in August 2006 with corrections to the Cover Date.     

Fast quantification of recombinant protein inclusion bodies within intact cells by FT-IR spectroscopy

The accomplishment of the quantification of the recombinant protein content of whole bacterial cells by FT-IR spectroscopy by application of chemometrics is shown. Recombinant Escherichia coli cells expressing an inclusion body forming fusion protein were dried on a 96-well silicon plate for the analysis in a high-throughput FT-IR spectrometer. Acquired spectra of additionally conventionally quantified samples were used to establish a multivariate calibration. The obtained method was tested by predicting inclusion body contents of samples not used for the multivariate model. Results from FT-IR spectra coincided well with the data of universalized electrophoresis analysis. Hence FT-IR spectroscopy could prove as a fast and simple alternative to conventional quantification methods.     

The detection of food soils on stainless steel using energy dispersive X-ray and Fourier transform infrared spectroscopy

Organic soiling is a major issue in the food processing industries, causing a range of biofouling and microbiological problems. Energy dispersive X-ray (EDX) and Fourier transform infra red spectroscopy (FT-IR) were used to quantify and determine the biochemical groups of food soils on stainless steel surfaces. EDX quantified organic material on surfaces where oily based residues predominated, but was limited in its usefulness since other food soils were difficult to detect. FT-IR provided spectral ‘fingerprints’ for each of the soils tested. Key soiling components were associated with specific peaks, viz. oils at 3025 cm^?1–3011 cm^?1, proteins at 1698 cm^?1–1636 cm^?1 and carbohydrates at 1658 cm^?1–1596 cm^?1, 783 cm^?1–742 cm^?1. High concentrations of some soils (10%) were needed for detection by both EDX and FT-IR. The two techniques may be of use for quantifying and identifying specific recalcitrant soils on surfaces to improve cleaning and hygiene regimes.     

Quantification of polymeric mannose in wine extracts by FT-IR spectroscopy and OSC-PLS1 regression

FT-IR spectroscopy has being a widespread technique in the agro-industry for the quick assess of food components, including the wine. Using the region of wavenumbers 1200–800 cm⁻¹ of the FT-IR spectra wine polysaccharides, Partial Least Squares Regression (PLS1) independent calibration models were built for mannose quantification in complex matrices from white and in red wine extracts. With PLS1 it was not possible to build a calibration model that included both white and red wine extracts. However, a predictive ability of the model for quantification of mannose from mannoproteins based on this FT-IR spectral region was achieved by the application of orthogonal signal correction (OSC)-PLS1.     

Comparison of three methods of DNA extraction from cold-smoked salmon and impact of physical treatments

AIMS: To compare three bacterial DNA extraction procedures on cold-smoked salmon (CSS) and assess the impact on their efficiency of two physical treatments of the food matrix, ionizing irradiation and freezing. METHODS AND RESULTS: As molecular methods for bacterial detection have become an important analytical tool, we compared bacterial DNA extraction procedures on CSS. Working with frozen and irradiated CSS, we obtained negative responses from samples known to be highly contaminated. Thus, we decided to study the impact of these two physical treatments on bacterial DNA extraction procedures. The efficiency of bacterial DNA extraction directly from the fish matrix suspension was measured by an rpoB PCR-based reaction. The results demonstrated that the DNeasy tissue extraction kit (Qiagen, Courtaboeuf, France) was the most efficient and reproducible method. We also showed that freezing and ionizing irradiation have a negative impact on DNA extraction. This was found probably not to be due to inhibition as the PCR reaction remained negative after adding BSA to the PCR mix reaction. CONCLUSIONS: The extraction kit was the most efficient method. Physical treatments were shown to hamper bacterial DNA extraction. SIGNIFICANCE AND IMPACT OF THE STUDY: Attention must be paid to molecular bacterial detection on food products subject to freezing or to ionizing irradiation.     

Interfacial properties of the M1 segment of the nicotinic acetylcholine receptor

We have studied the thermodynamic, surface, and structural properties of alphaM1 transmembrane sequence of the nicotinic acetylcholine receptor (nAChR) by using Langmuir monolayer, FT-IR spectroscopy and molecular dynamics simulation techniques in membrane-mimicking environments. M1 spontaneously incorporates into a lipid-free air-water interface, showing a favourable adsorption free energy of -7.2 kcal/mol. A cross-sectional molecular area of 210 A(2)/molecule, a surface potential of 4.2 fV/molecule and a high stability of the film were deducted from pure M1 monolayers. FT-IR experiments and molecular dynamics simulations in membrane-mimicking environments (sodium-dodecyl-sulfate and CCl(4), respectively) indicate coexistence between helical and non-helical structures. Furthermore, mixed peptide-lipid monolayers and monolayer penetration experiments were performed in order to study the peptide-lipid interaction. Mixed with condensed lipids (dipalmitoyl-phosphocholine, and dipalmitoyl-phosphoglycerol), M1 shows immiscible/miscible behaviour at low/high peptide concentration, respectively. Conversely, a complete miscible peptide-lipid interface is observed with liquid-expanded lipids (palmitoyl-oleoyl-phosphocholine, and palmitoyl-oleoyl-phosphoglycerol). Peptide penetration experiments demonstrate that the M1 peptide preferentially interacts with zwitterionic phosphocholine interfaces.     

Production of organic acids by probiotic lactobacilli can be used to reduce pathogen load in poultry

Probiotic Lactobacillus can be used to reduce the colonization of pathogenic bacteria in food animals, and therefore reduce the risk of foodborne illness to consumers. As a model system, we examined the mechanism of protection conferred by Lactobacillus species to inhibit C. jejuni growth in vitro and reduce colonization in broiler chickens. Possible mechanisms for the reduction of pathogens by lactobacilli include: 1) stimulation of adaptive immunity; 2) alteration of the cecal microbiome; and, 3) production of inhibitory metabolites, such as organic acids. The Lactobacillus species produced lactic acid at concentrations sufficient to kill C. jejuni in vitro. We determined that lactic acid produced by Lactobacillus disrupted the membrane of C. jejuni, as judged by biophotonics. The spectral features obtained using Fourier-transform infrared (FT-IR) and Raman spectroscopy techniques were used to accurately predict bacterial viability and differentiate C. jejuni samples according to lactic acid treatment. FT-IR spectral features of C. jejuni and Lactobacillus grown in co-culture revealed that the metabolism was dominated by Lactobacillus prior to the killing of C. jejuni. Based on our results, the development of future competitive exclusion strategies should include the evaluation of organic acid production.     

Bacteria and archaea as the sources of traits for enhanced plant phenotypes

Rising global demand for food and population increases are driving the need for improved crop productivity over the next 30 years. Plants have inherent metabolic limitations on productivity such as inefficiencies in carbon fixation and sensitivity to environmental conditions. Bacteria and archaea inhabit some of the most inhospitable environments on the planet and possess unique metabolic pathways and genes to cope with these conditions. Microbial genes involved in carbon fixation, abiotic stress tolerance, and nutrient acquisition have been utilized in plants to enhance plant phenotypes by increasing yield, photosynthesis, and abiotic stress tolerance. Transgenic plants expressing bacterial and archaeal genes will be discussed along with emerging strategies and tools to increase plant growth and yield.     

蔊菜杂草性的研究

本文通过对十字花科常见杂草芹菜[Rorippa in lica(L.)Hiern]在南京地区的自然群体的周期性观察,以了解其在不同生态环境下的生活周期。本文还通过一系列实验来观察其繁育系统、种子传播的动因、结实力、种子发芽率和植物抗人为干扰的耐受性。花蕾套袋试验证明蔊菜主要是自交可亲和的,即使存在异型杂交也是微不足道的。种子传播效应试验揭示水和风都是种子传播的自然力。该种具有范围很广的耐受性,踏践和刈割试验证明在严重的人为于扰下仍能完成其生活周期。蔊菜尽管本质上属于多年生草本,能产生大量的种子,在很大程度上靠种子繁殖。种子萌芽试验证明它的种子萌发参差不齐。总之,蔊菜具有典型杂草的许多特性,而这些特性给它以适合在多种自然的和人为干扰的环境中正常地生长的能力。     

Rapid and quantitative detection of the microbial spoilage of meat by fourier transform infrared spectroscopy and machine learning

Fourier transform infrared (FT-IR) spectroscopy is a rapid, noninvasive technique with considerable potential for application in the food and related industries. We show here that this technique can be used directly on the surface of food to produce biochemically interpretable "fingerprints." Spoilage in meat is the result of decomposition and the formation of metabolites caused by the growth and enzymatic activity of microorganisms. FT-IR was exploited to measure biochemical changes within the meat substrate, enhancing and accelerating the detection of microbial spoilage. Chicken breasts were purchased from a national retailer, comminuted for 10 s, and left to spoil at room temperature for 24 h. Every hour, FT-IR measurements were taken directly from the meat surface using attenuated total reflectance, and the total viable counts were obtained by classical plating methods. Quantitative interpretation of FT-IR spectra was possible using partial least-squares regression and allowed accurate estimates of bacterial loads to be calculated directly from the meat surface in 60 s. Genetic programming was used to derive rules showing that at levels of 10(7) bacteria.g(-1) the main biochemical indicator of spoilage was the onset of proteolysis. Thus, using FT-IR we were able to acquire a metabolic snapshot and quantify, noninvasively, the microbial loads of food samples accurately and rapidly in 60 s, directly from the sample surface. We believe this approach will aid in the Hazard Analysis Critical Control Point process for the assessment of the microbiological safety of food at the production, processing, manufacturing, packaging, and storage levels.